Don't need spark plugs or wires yet . I change oil and filter every 50 hours . I use Mobil 1 15w50 in all my boats . The 15w50 is whats recommended by Mobil for both roller and flat lifter engines. I also change the trans oil every 50 hours. Don't look for problems if you don't have any . The best advice I can give anyone is If it ain't broke don't fix it.